Valves may be employed in any one of numerous situations. For example, valves may be used in an air distribution system to direct airflow from one portion of an aircraft to another. In this regard, pneumatic valves may be disposed in a duct between an air source and one or more outlets for exhausting the received air to desired areas within the aircraft, such as, for example, to an aircraft cabin or an underfloor section of the aircraft.
One exemplary type of pneumatic valve that has been employed in aircraft is a butterfly valve. A butterfly valve is typically made up of a valve flowbody and a butterfly plate. The valve flowbody may be made of a rigid material, such as metal, and includes an inner surface defining a channel. The valve flowbody is configured to be disposed between two ducts or disposed in a portion of a single duct. The butterfly plate is made of a rigid material as well and is rotationally mounted to the valve flowbody. Conventionally, the butterfly plate is positioned in the channel such that a minimum clearance is formed with the inner surface of the valve flowbody. An actuator and a spring may be used to control the rotation of the butterfly plate.
Typically, the butterfly plate is moved between closed, open, and partially open positions. When in the closed position, the butterfly plate substantially blocks the channel to prevent, or at least inhibit, fluid from flowing therethrough. When fluid flows through the valve flowbody in a forward direction, the butterfly plate moves to the open or partially open position to allow fluid flow through the channel. An actuator is typically used as a control device to mechanically cause the disk of a butterfly valve to rotate. Actuators can be either manual or automatic and operated by hand, electronics, pneumatics, hydraulics, or springs.
Some butterfly valves include a serrated spline coupling to couple the butterfly valve to the actuator. In an embodiment of this type, an electromechanical actuator is used to drive a valve shaft of the butterfly valve via an actuator output shaft and the serrated spline coupling. The serrated spline coupling provides for the transfer of torque from the actuator to the valve shaft though rotary motion of the actuator output shaft.
Although the aforementioned valve configuration including a serrated spline coupling operates adequately, it may exhibit some drawbacks. For example, when the valve is operational, misalignment at the serrated spline interface, and more particularly at an interface between the actuator output shaft and the butterfly valve shaft, may occur. More specifically, the flow of fluid through the valve flowbody may cause differential pressure across the butterfly plate causing the butterfly valve shaft to deflect (bow) between a ball bearing that supports the butterfly valve shaft on either side of the butterfly plate. The deflection of the butterfly valve shaft may cause radial and angular misalignment at the serrated spline interface. The misalignment may lead to binding at the interface of the butterfly valve shaft and the actuator output shaft as well as generate substantial side loads that may be transferred into the output shaft of the actuator. This misalignment at the spline interface may additionally cause the motor of the actuator to stall or overload the gear train in an output section and result in increased wear. In some cases, in addition to misalignment at the spline interface, the thrust and radial loads generated by the butterfly plate must be properly distributed through a bearing system to minimize the occurrence of valve malfunction.
Accordingly, there is a need for a butterfly valve that includes a means for constraining forces exerted upon an interface that exist at a serrated spline interface, between an actuator output shaft and a butterfly valve shaft. More specifically, there is a need for a means to minimize misalignment of an actuator output shaft and a butterfly valve shaft at the serrated spline interface. In addition, it would be desirable for the valve to have an increased life expectancy, to be lightweight, and to be relatively inexpensive to implement. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background